The best strategy for preventing the continuing spread of infection with the human immunodeficiency virus (HIV) involves the development of an effective vaccine. Herpes simplex virus (HSV) amplicons represent a novel and promising strategy for vaccine development. HSV amplicons maintain several advantages as a vaccine strategy. First, HSV amplicons cannot cause any infectious disease. Second, HSV amplicons have a wide host cell tropism and are able to efficiently enter multiple cell types including mucosal cells. Third, HSV amplicons have a large coding capacity, which allows for the development of vectors that could encode multiple antigens and/or immunostimulatory gene products. Finally, HSV amplicons do not contain the immunomodulatory genes that are a part of replication-defective or attenuated HSV delivery systems. Previous studies with HSV amplicons have been performed in small animal model systems. However, the immunogenicity of these amplicons has never been tested in a non-human primate model system. The studies described in this proposal will determine if HSV amplicons can elicit a significant immune response in the rhesus macaque. Specifically, rhesus macaques will be inoculated via an intramuscular route with HSV amplicons that express the SIVmac239 gag gene product or by control amplicons that do not express any SIV gene product. The cellular immune response to Gag will be followed through analysis of CD4+ and CD8+ T cell responses, tetramer staining, and antigen-specific cytokine production. The humoral response will be determined by analysis of both serum and mucosal immunity. Finally, the innate immune response will be determined through analysis of both natural killer cells and by performing longitudinal studies of changes in lymphocyte proliferation and activation. Successful completion of these studies will allow for efficacy trials to be initiated in the SIV model system. Future studies may be extended to utilize HSV as a vaccine delivery system to prevent HIV infection of humans. In addition, the successful completion of these studies will have a significant impact on the continued development of HSV amplicons as gene and cancer therapy vectors.